Various materials have been incorporated in organopolysiloxane compositions to improve the thermal conductivity of the resultant elastomers. Boron nitride, for example, has been added to organopolysiloxane compositions, such as those described in U.S. Pat. No. 3,499,859 to Matherly to form thermally conductive room temperature vulcanizable silicone elastomers. Also, U.S. Pat. No. 4,292,225 to Theodore et al describes highly filled organopolysiloxane compositions containing boron refractory powders to provide silicone elastomers having good thermally conductive properties.
In contrast to the teachings of U.S. Pat. Nos. 3,499,859 and 4,292,225, it has been found that organopolysiloxane compositions containing silicon nitride particles provide elastomers having desirable physical properties as well as excellent thermal conductivity. Moreover, the compositions of this invention are useful for insulating electrical components while they permit any heat which is generated to be conducted away from the electrical component. Furthermore, the compositions of this invention are unique in that increased filler loadings can be achieved using silicon nitride particles and the resultant elastomers have superior thermal conductivity and desirable physical properties.
It is, therefore, an object of this invention to provide a highly filled thermally conductive vulcanizable silicone elastomer containing silicon nitride particles. Another object of this invention is to provide a thermally conductive organopolysiloxane composition having unique physical properties by virtue of the fact that silicon nitride particles can be used in higher filler loadings than many other conventional thermally conductive materials. Still another object of this composition is to provide a highly filled composition which is sufficiently pliable that it can be extruded and cured. A further object of this invention is to provide highly filled silicone elastomers having improved thermal conductivity.